We synthesized a self-healing polyurethane elastomer (PU-SSDA) which displayed excellent healing efficiency at room temperature due to the synergistic contribution of dynamic covalent D-A bond and S–S bond. Mechanical and self-healing properties of the polyurethane elastomers were characterized by tensile test and three-dimensional super depth of field microscope. The cross-linking structure of PU-SSDA is explored by extraction experiments
demonstrating that there are not only crosslinked structures but also linear molecular segments existed in the polyurethane elastomer. Mechanical properties of the PU-SSDA elastomer can be tuned by changing the cross-linking degree. As the crosslinking degree increases from 25% to 45%
the tensile strength increases from 2.9 MPa to 5.5 MPa while the elongation at break decreases from 795% to 304%. After optimization
when the crosslinking degree was 35%
the tensile strength was 3.7 MPa
the elongation at break was 606% and the repair efficiency could be restored to 93% after healing for 60 min at room temperature. Moreover
the healing efficiency still remains above 90% after 4 damage-healing cycles. In addition
the PU-SSDA elastomer can also be reprocessed by hot pressing at 120 °C. This excellent self-healing behavior and reprocessable property were attributed to the reversible fracture recombination reaction of dynamic D-A and S―S bonds and the quick infiltration of the linear polymer chains into damaged surface. The self-healing mechanism can be further confirmed by the dissolution experiments which showed that the PU-SSDA elastomer can be dissolved in DMF at 100 °C while the PU-control can only swell under the same conditions
demonstrating that the reversible cleavage and reformation of D-A and S―S bonds contribute a lot to the self-healing process. Due to the facile and friendly preparation method
fast self-healing behavior at room temperature and fully reprocessable properties
the as-prepared polyurethane elastomers displayed wide potential applications such as protection coatings and wearable electronic devices.
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